import { CheckedExpr, CheckedType } from "./checked.ts";
import { ParsedExpr } from "./parsed.ts";
import { CompileError } from "./token.ts";

export type SymbolValue = {
    id: number;
    subject: string;
    valueType: CheckedType;
};

export class SymbolTable {
    private idCounter = 0;
    private symbols: { [key: string]: SymbolValue } = {};

    public define(subject: string, valueType: CheckedType) {
        if (subject in this.symbols) {
            throw new Error("redefinition not implemented");
        }
        const id = this.idCounter;
        this.idCounter++;
        this.symbols[subject] = { id, subject, valueType };
    }
}

export class Checker {
    private symbolTable = new SymbolTable();
    public errors: CompileError[] = [];

    public check(statements: ParsedExpr[]): CheckedExpr[] {
        return statements as CheckedExpr[];
    }

    private searchTopLevelStatements(statements: ParsedExpr[]) {
        for (const statement of statements) {
            switch (statement.exprType) {
                case "fn":
                    this.searchTopLevelFn(statement);
                    break;
                case "let":
                    break;
                default:
                    this.errors.push({
                        pos: statement.pos,
                        message:
                            `statement '${statement.exprType}' not supported in top level`,
                    });
                    break;
            }
        }
    }

    private searchTopLevelFn(statement: ParsedExpr & { exprType: "fn" }) {
    }
}